1. Field of the Invention
The present invention relates generally to light emitting diodes (LEDs), and more particularly, to an LED illuminating device.
2. Description of the Related Art
While a conventional high-power LED is working, it generates high heat. However, none of any better solution to improvement of the dissipation of such heat has been proposed. Particularly, the illuminating device based on such high-power LED will fail to be applied to the daily life of people if the dissipation of the high heat cannot be effectively improved.
U.S. Pat. No. 5,173,839 disclosed a heat-dissipating method of an LED display, in which the LED chip is composed of a thermally conductive tape, an aluminum strip, and a heat sink. The heat generated by the LED chip is partially transmitted outside from a lower side of the LED chip. However, three medium layers are located between the LED chip and the heat sink where the other primary part of the heat is generated, such that the number of the medium layers is so big that the thermal resistance is greater to incur worse efficiency of thermal dissipation.
Further, as disclosed in U.S. Patent Laid-Open No 2006/0098449, an LED is mounted on a flat portion of one end of a heat pipe, and however the flat portion has limited area, such that only few LEDs can be mounted on the flat portion. As known from the drawings, the LED is mounted onto the heat pipe via a base, or a plurality of LEDs are mounted on the same heat pipe via the same base. However, the thermal resistance will still be high if the base is used as the medium layer for thermal conduction. Although it takes advantage of the isothermal performance of the heat pipe for good thermal dissipation, only the flat surface of one end of the heat pipe is available for mounting the LEDs thereto, so the number and the position of the LEDs are restricted. When this heat-dissipating method is applied to the illuminating device, the thermal dissipation of the illuminating device is not effective, so that the range of its application is small and there is some space for improvement. In addition to the method, even if the heat pipe is also applied to the illuminating device, because a very thick base is still located between the LEDs and the heat pipe, under the condition of high thermal resistance, the enhancement of efficiency of the thermal dissipation is still limited. Further, the area of the LEDs is also limited because the heat pipe is mounted to the LEDs.